tip-up

tip-up (not comparable)

1. (of a seat) Designed to tilt to a vertical position when not in use, either manually or of its own accord.
   • 1961 October, “New Metropolitan Line train sets enter service”, in Trains Illustrated, page 623:

     [...] there is no permanent division between the guard's section, which contains four tip-up seats, and the main passenger saloon.

• “tip-up” in Lexico, Dictionary.com; Oxford University Press.